Digital X-ray tomosynthesis generates retrospective reconstructed three-dimensional (3D) planar images of anatomy/structure from a series of two-dimensional (2D), low-dose projections that are acquired within a limited angular range. Retrospective reconstruction not only provides depth information of the anatomy/structure that is otherwise unavailable in the conventional 2D radiographs, but also enhances image contrast due to advanced image processing techniques.
However, the full benefit of digital tomosynthesis has not yet been achieved due to the existence of the out-of-focus artifacts. These artifacts present as a “ghost” shadow in the image that alters the background and consequently lowers the contrast of the anatomy/structure of interest. The artifact may present as a false object and could mislead diagnosis. The main cause of the artifact is the limited angular range of acquisition that results in incomplete view sampling of the object space. The problem of reconstruction of the original anatomy/structure is essentially an unsolved under-determined least square problem. Solving under-determined least squares in images is mathematically very difficult and the exact solution does not exist given the amount of unknowns.
One solution is to increase the angular range at acquisition. However, this solution is usually extremely difficult due to many practical reasons.